The first guy that got infected was sent home by his local GP, then later went to the hospital and got sent home a second time, neither one catching that he had the virus. So he walked around infecting people for two weeks or so - and now his hometown and the province around it are ground zero for the virus in Italy.

There are Chinese investments in the BRI all over the world, especially in Africa and Asia, often with the physical labour being handled by Chinese migrant workers - so far, it doesn't seem like they're a significant source of infections anywhere that I've seen. Mostly because all the ones who went home for the Chinese New Year holidays, have stayed home due to the virus outbreak.